1. Field of the Invention
The present invention relates to a method and related system of detecting a transmission channel in a wireless communication system, and more particularly, to a method and related system of detecting a transmission channel by recording a result of a cross correlation operation.
2. Description of the Prior Art
In a wireless communication system, wireless signals are assumed to be transmitted over a steady transmission channel. As a matter of fact, the transmission channel may change abruptly since the distance between two communication devices is changed or there is an obstacle between the communication devices. However, abrupt change of the transmission channel could result in false outcomes of some algorithms. For example, a rate adaptation algorithm is used for measurements of packet error rate within a fixed period of time. Once the abrupt change of the transmission channel occurs, the packet error rate obtained from the rate adaptation algorithm cannot reflect the current channel condition accurately, causing the rate adaptation algorithm no more reliable. Thus, it is important in the wireless communication system to detect the abrupt change of the transmission channel.
In the prior art, the abrupt change of the transmission channel is detected by using the energy of received signals. The spectrum of the received signal is filtered into several sub-bands. A time interval of interest corresponding to each sub-band is divided into two sections. For each band, a time position of dividing the time interval is determined to be a division position resulting in maximum difference of average energy between the sections. If the time positions of division corresponding to each sub-band are located at the same position or in the neighboring hood, the abrupt change of the transmission channel is declared.
However, the abrupt change of the transmission channel may not involve in energy change of the received signals. In this situation, the prior art can not accurately detect the change of the transmission channel. Further, in practice, it has high complexity to determine the time positions of division for each sub-band by finding maximum differences of average energy between two sections of the time interval. Consequently, the cost will rise accordingly.
To sum up, when the change of the transmission channel does not involve in energy changes of received signals, the prior art can not accurately detect whether there is any abrupt change over the transmission channel. In addition, the cost increases due to high complexity in practice.